Substrate processing apparatus and method for manufacturing a semiconductor device

ABSTRACT

A CVD device has a reaction furnace ( 39 ) for processing a wafer ( 1 ); a seal cap ( 20 ) for sealing the reaction furnace ( 39 ) hermetically; an isolation flange ( 42 ) opposite to the seal cap ( 20 ); a small chamber ( 43 ) formed by the seal cap ( 20 ), the isolation flange ( 42 ), and the wall surface in the reaction furnace ( 39 ); a feed pipe ( 19   b ) for supplying a first gas to the small chamber ( 43 ); an outflow passage ( 42   a ) provided in the small chamber ( 43 ) for allowing the first gas to flow into the reaction furnace ( 39 ); and a feed pipe ( 19   a ) provided downstream from the outflow passage ( 42   a ) for supplying a second gas into the reaction furnace ( 39 ). Byproducts such as NH4Cl are prevented from adhering to low temperature sections such as the furnace opening and therefore the semiconductor device production yield is therefore increased.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/528,137, filed Dec. 12, 2005 U.S. Pat. No. 8,057,599, whichapplication is a 35 U.S.C. 371 of International Application No.PCT/JP04/01996, filed Feb. 20, 2004, which application claims priorityof Japanese Application No. 2003-44049, filed Feb. 21, 2003, JapaneseApplication No. 2003-44904, filed Feb. 21, 2003, Japanese ApplicationNo. 2003-87966, filed Mar. 27, 2003, and Japanese Application No.2003-87884, filed Mar. 27, 2003, all of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a substrate processing apparatus forprocesses such as forming thin films on substrates includingsemiconductor substrates and glass substrates, and a manufacturingmethod for semiconductor devices including processes such as formingthin films on substrates.

BACKGROUND ART

In upright thermal CVD device that performs processes such as formingSi3N4 film on the multiple substrates by utilizing dichlorosilane(SiH2Cl2) and ammonia (NH3), other than the silicon nitride (Si3N4) filmcomprising the target film, byproducts such as ammonium chloride (NH4Cl)are generated and adhere to low temperature sections such as the wallsurface inside the furnace opening at the lower section of the reactionfurnace. These adhering byproducts are a source of particles and createproblems. One method for resolving this problem is a technique forheating low temperature sections such as the furnace opening on thelower section of the reaction furnace to an extent where the byproductswill not adhere (see for example Japanese Patent Non-ExaminedPublication No. 2002-184769).

However, there are temperature limits even on this heating method due tothe O-ring for sealing between the reaction furnace and the furnaceopening seal cap for sealing the reaction furnace, and the rotationmechanism for rotating the boat inside the reaction furnace in thevicinity of the furnace opening. Technology is therefore required forpreventing byproducts such as NH4Cl from adhering to low temperaturesections such as the furnace opening, without heating.

In order to resolve the above problems with the prior art, the presentinvention has the object of preventing byproducts such as NH4Cl fromadhering to low temperature sections such as the furnace opening,without applying heat.

DISCLOSURE OF INVENTION

In the present invention, a first gas is supplied to a small chamber(space) formed by covering the upper surface of the seal cap by thecover, and the first gas purges the small chamber by flowing from thesmall chamber into the reaction furnace, and a second gas is supplieddownstream of the first gas flow. The second gas is in this wayprevented from the flowing into the small chamber so that the generationof byproducts created by the first gas and second gas mixing at a lowtemperature in the vicinity of the furnace opening of the reactionfurnace can be prevented. Byproducts can in this way be prevented fromadhering in the vicinity of the furnace opening of the reaction furnace.

Characteristic features of the present invention disclosed in thesespecifications are as follows.

(1) A substrate processing apparatus comprising: a reaction furnace forprocessing a substrate; a seal cap for sealing the reaction furnacehermetically; a cover installed separately from the seal cap so as tocover at least a section of the surface of the seal cap facing the innerside of the reaction furnace; a small chamber formed at least by theseal cap and the cover; a feed opening for supplying a first gas to thesmall chamber; a flow outlet provided in the small chamber for makingthe first gas flow into the reaction furnace; and a feed openingprovided further downstream than the flow outlet, for supplying a secondgas into the reaction furnace.

(2) The substrate processing apparatus according to one embodiment,wherein the small chamber is formed by the seal cap and the cover andthe inner wall surface of the reaction furnace; and the flow outlet isformed by a clearance between the cover and the inner wall surface ofthe reaction furnace.

(3) The substrate processing apparatus according to another embodiment,wherein the reaction furnace includes a process tube, and a furnaceopening flange for supporting the process tube; and the small chamber isformed by the seal cap and the cover and the inner wall surface of thefurnace opening flange; and the flow outlet is formed by a clearancebetween the inner wall surface of the furnace opening flange and thecover.

(4) The substrate processing apparatus according to another embodiment,wherein the furnace opening flange includes an inlet flange forsupporting the process tube, and a base flange for supporting the inletflange; and the small chamber is formed by the inner wall surface of thebase flange and the cover and the seal cap; and the flow outlet isformed by a clearance between the inner wall surface of the base flangeand the cover.

(5) The substrate processing apparatus according to another embodiment,wherein the feed opening for supplying the first gas is provided in thebase flange; and the feed opening for supplying the second gas isprovided in the inlet flange.

(6) The substrate processing apparatus according to another embodiment,wherein the cover is formed by a plate-shaped member.

(7) The substrate processing apparatus according to another embodiment,comprising a boat for holding multiple substrates approximatelyhorizontally at intervals in multiple stages, and a rotation mechanismfor supporting and rotating the boat by way of a rotating shaftpenetrating through the seal cap, wherein the cover is installed in therotating shaft.

(8) The substrate processing apparatus according to another embodiment,wherein the first gas is ammonia, the second gas is dichlorosilane, anda silicon nitride film is formed on the substrate by the thermal CVDmethod in the processing.

(9) A substrate processing apparatus comprising: a reaction furnace forprocessing a substrate; a seal cap for sealing the reaction furnacehermetically; a first cover installed separately from the seal cap so asto cover at least a section of the surface of the seal cap facing theinner side of the reaction furnace; a first small chamber formed by theseal cap and the first cover, a first feed opening for supplying a firstgas to the first small chamber; a first flow outlet provided in thefirst small chamber for making the first gas flow into the reactionfurnace; a second cover installed separately from the inner wall surfaceof the lower section of the reaction furnace so as to cover at least aportion of the inner wall surface of the lower part of the reactionfurnace; a second small chamber formed by the second cover and the innerwall surface of the lower part of the reaction furnace; a second feedopening for supplying a second gas to the second small chamber; and asecond flow outlet provided in the second small chamber for allowing thesecond gas to flow into the reaction chamber.

(10) The substrate processing apparatus according to another embodiment,wherein a ring-shaped member is installed on the seal cap, the firstsmall chamber is formed by the seal cap and the first cover and thering-shaped member; and the second small chamber is formed by the innerwall surface of the lower part of the reaction furnace and the secondcover and the ring-shaped member.

(11) The substrate processing apparatus according to another embodiment,wherein the first flow outlet is formed by a clearance between the firstcover and the ring-shaped member; and the second flow outlet is formedby a clearance between the second cover and the ring-shaped member.

(12) The substrate processing apparatus according to another embodiment,comprising a boat for holding multiple substrates approximatelyhorizontally at intervals in multiple stages, wherein the reactionfurnace includes a process tube comprised of an inner tube and an outertube, and a furnace opening flange for supporting the process tube; andthe first cover is comprised of an end plate on the lower side of theboat, and the second cover is comprised of an extending section of theinner tube extending downwards from the protrusion for installing theinner tube on the furnace opening flange.

(13) The substrate processing apparatus according to another embodiment,wherein there is no metal member inside the reaction furnace for mixingthe first gas flowing from the first flow outlet with the second gasflowing from the second flow outlet.

(14) The substrate processing apparatus according to another embodiment,wherein the first feed opening for supplying the first gas is formed bya clearance between the seal cap and the rotating shaft.

(15) The substrate processing apparatus according to another embodiment,wherein the first gas is ammonia, and the second gas is dichlorosilane,and a silicon nitride film is formed on the substrate by the thermal CVDmethod in the processing.

(16) substrate processing apparatus comprising: a reaction furnace forprocessing a substrate; a seal cap for sealing the reaction furnacehermetically; a first cover installed separately from the seal cap so asto cover at least a section of the surface of the seal cap facing theinner side of the reaction furnace; a first small chamber formed by theseal cap and the first cover, a first feed opening for supplying a firstgas to the first small chamber; a first flow outlet provided in thefirst small chamber for making the first gas flow into the reactionfurnace; a second cover installed separately from the inner wall surfaceof the lower section of the reaction furnace so as to cover at least aportion of the inner wall surface of the lower part of the reactionfurnace; a second small chamber formed by the second cover and the innerwall surface of the lower part of the reaction furnace; a second feedopening for supplying a second gas to the second small chamber; and asecond flow outlet provided in the second small chamber for allowing thesecond gas to flow into the reaction chamber, and a third feed openingprovided further downstream than the first flow outlet and the secondflow outlet for supplying a third gas into the reaction furnace.

(17) The substrate processing apparatus according to another embodiment,wherein the first gas and the second gas are ammonia, and the third gasis dichlorosilane, and a silicon nitride film is formed on the substrateby the thermal CVD method in the processing.

(18) A semiconductor device manufacturing method comprising the stepsof: loading a substrate into a reaction furnace; sealing the reactionfurnace hermetically with a seal cap; processing the substrate bysupplying a first gas into a small chamber formed by the seal cap and acover installed separately from the seal cap so as to cover at least asection of the surface of the seal cap facing the inner side of thereaction furnace, along with making the first gas flow into the reactionfurnace from a flow outlet provided in the small chamber, and supplyinga second gas into the reaction furnace from a second feed openingprovided further downstream than the flow outlet; and unloading thesubstrate from the reaction furnace.

(19) A semiconductor device manufacturing method comprising the stepsof: loading a substrate into a reaction furnace; sealing the reactionfurnace hermetically with a seal cap; processing the substrate bysupplying a first gas into a small chamber formed by the seal cap and afirst cover installed separately from the seal cap so as to cover atleast a section of the surface of the seal cap facing the inner side ofthe reaction furnace, along with allowing the first gas to flow into thereaction furnace from a flow outlet provided in the small chamber,supplying a second gas into a second small chamber formed by the innersurface of the lower section of the reaction furnace and a second coverinstalled separately from the inner surface of the lower section of thereaction furnace so as to cover at least a section of the inner surfaceof the lower section of the reaction furnace, and making the second gasflow into the reaction furnace from a second flow outlet provided in thesecond chamber; and unloading the substrate from the reaction furnace.

(20) A semiconductor device manufacturing method comprising the stepsof: loading a substrate into a reaction furnace; sealing the reactionfurnace hermetically with a seal cap; processing the substrate bysupplying a first gas into a small chamber formed by the seal cap and afirst cover installed separately from the seal cap so as to cover atleast a section of the surface of the seal cap facing the inner side ofthe reaction furnace, along with allowing the first gas to flow into thereaction furnace from a flow outlet provided in the small chamber,supplying a second gas into a second small chamber formed by the innersurface of the lower section of the reaction furnace and a second coverinstalled separately from the inner surface of the lower section of thereaction furnace so as to cover at least a section of the inner surfaceof the lower section of the reaction furnace, allowing the second gas toflow into the reaction furnace from a second flow outlet provided in thesecond chamber, and supplying a third gas into the reaction furnace fromfurther downstream than the first flow outlet and the second flowoutlet; and unloading the substrate from the reaction furnace.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a frontal cross sectional view showing the reaction furnace ofthe substrate processing apparatus of the first embodiment of thepresent invention;

FIG. 2 is a frontal cross sectional view showing the furnace opening indetail;

FIG. 3A is an enlarged cross sectional view showing the flow outletsection in detail;

FIG. 3B is an enlarged cross sectional view showing the flow outletsection gas flow;

FIG. 4 is a frontal cross sectional view showing in detail, the furnaceopening of the reaction furnace of the substrate processing apparatus ofthe second embodiment of the present invention;

FIG. 5A is an enlarged cross sectional view showing that labyrinth sealsection in detail;

FIG. 5B is an enlarged cross sectional view showing the gas flow in thatsection;

FIG. 6 is a frontal cross sectional view showing in detail, the furnaceopening of the reaction furnace of the substrate processing apparatus ofthe third embodiment of the invention;

FIG. 7 is an enlarged cross sectional view showing the gas flow in thatdivider ring section;

FIG. 8 is a frontal cross sectional view showing in detail, the furnaceopening of the reaction furnace of the substrate processing apparatus ofthe fourth embodiment of the invention;

FIG. 9 is a frontal cross sectional view showing in detail, the furnaceopening of the reaction furnace of the substrate processing apparatus ofthe fifth embodiment of the invention;

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention are next described whilereferring to the drawings.

The CVD device shown in FIG. 1 and FIG. 2 is provided with an uprightprocess tube 11 fixedly installed perpendicular with the vertical centerline. This process tube 11 contains an inner tube 12 and an outer tube13. The inner tube 12 is formed in an integrated tubular shape utilizingquartz glass or silicon carbide (SiC). The outer tube 13 is formed in anintegrated tubular shape utilizing quartz glass or silicon carbide. Theinner tube 12 is formed in a tubular shape, and the top and bottom areopened. A processing chamber 14 of a reaction furnace 39 loaded withmultiple wafers 1 supported in an array vertically by a boat 21(described later) is formed inside the hollow tube of the inner tube 12.The lower end opening of the inner tube 12 forms a furnace opening 15for loading and unloading the wafers 1 as the processing substrates. Theinside diameter of the inner tube 12 is therefore set to a diameterlarger than the maximum outside diameter of the wafers 1. The insidediameter of the outer tube 13 is larger than the outside diameter of theinner tube 12, and is formed in a tubular shape sealed at the top endand open at the bottom end. The inside tube 12 is covered byconcentrically by the outer tube 13 that encloses the outer side of theinner tube 12.

The space between the bottom end of the inner tube 12 and the bottom endof outer tube 13 is sealed hermetically by a metallic (for examplestainless steel) furnace opening flange 16 formed in a circular ringshape. The furnace opening flange 16 is supported by a case 31 of theCVD device so that the process tube 11 is installed upright. The furnaceopening flange 16 is made up of an inlet flange (manifold) 16 a forsupporting the process tube 11, and a base flange 16 b for supportingthe inlet flange 16 a. The inlet flange 16 a and the base flange 16 bare both made from metal (for example stainless steel). The inlet flange16 a of the furnace opening flange 16 in FIG. 1 is supported by the case31, and the base flange 16 b is also supported by the case 31 (omittedin FIG. 1 for purposes of simplicity).

An exhaust pipe 17 connected to an exhaust device (not shown in drawing)such as a vacuum pump, is connected to the upper section of the sidewall of the furnace opening 16. The exhaust pipe 17 connects to anexhaust path 18 formed by the clearance between the inner tube 12 andthe outer tube 13. The cross sectional shape of the exhaust path 18 is acircular ring shape of a fixed width, formed by the clearance betweenthe inner tube 12 and the outer tube 13. The exhaust pipe 17 connects tothe furnace opening flange 16 and therefore is arranged at the lowermostedge of the exhaust path 18.

A gas feed pipe 19 a at the bottom on the side wall of the inlet flange16 a of the furnace opening flange 16, connects to the furnace opening15 of the inner tube 12. A supply source (not shown in the drawing) suchas for SiH2Cl2 gas or inert gas is connected as the second gas(described later on) to the gas feed pipe 19 a. Therefore, the tipopening (blow vent) of the gas feed pipe 19 a forms a feed opening forsupplying the second gas into the reaction furnace. A gas feed pipe 19 bat the bottom on the side wall of the base flange 16 b of the furnaceopening 16, connects to the furnace opening 15 of the inner tube 12. Thegas feed pipe 19 b is connected to a supply source (not shown in thedrawing) such as for NH3 gas or inert gas as the first gas (describedlater). The tip opening (blow vent) of the gas feed pipe 19 b thereforeforms a feed opening for supplying the first gas to the small chamber.The gases that the gas feed pipes 19 a, 19 b supply to the furnaceopening 15 are exhausted from the exhaust pipe 17 via the exhaust path18 flowing in the processing chamber 14 of inner tube 12.

A metallic (for example stainless steel) seal cap 20 for sealing theprocessing chamber 14, makes direct contact with the lower end of thebase flange 16 b of the furnace opening flange 16 from the lower sidevia an O-ring 20 a. The seal cap 20 is formed in a disk shape with anoutside diameter equivalent to the furnace opening flange 16. The sealcap 20 is moved up and down by a boat elevator (not shown in drawing). Arotation mechanism (rotating shaft motor) 40 for rotating a boat 21(described later) is installed at the seal cap 20 so that a rotatingshaft (R shaft) 41 passes through the seal cap 20. An isolation flange42 functioning as a cover for covering the entire surface at theprocessing chamber 14 side of the seal cap 20 is installed to rotate asone piece with the rotating shaft 41. The rotating shaft 41 and theisolation flange 42 are both made of metal (for example high nickelalloys with high corrosion resistance such an alloy of 50 percent ormore nickel, 15 to 30 percent chromium, and 15 to 30 percent or moremolybdenum).

In the state (boat loading) in which the boat 21 is loaded into theprocessing chamber 14 of the reaction furnace 39 as shown in FIG. 2, asmall chamber 43 is formed by the lower surface of the isolation flange42, the upper surface of the seal cap 20, and the inner circumferentialsurface of the base flange 16 b. The gas feed pipe 19 b installed on thebase flange 16 b connects to this small chamber 43. A ring-shapedprotrusion 16 c is formed protruding to the inner side on the uppersection of the inner circumferential surface of the base flange 16 b.The isolation flange 42 is installed below this protrusion 16 c at aposition with somewhat of a clearance. The diameter of the isolationflange 42 is smaller than the inside diameter of the base flange 16 b,and larger than the internal diameter of the protrusion 16 c of the baseflange 16 b. As shown in FIG. 3A, a slight clearance C1 of approximately0.5 to 1.5 millimeters is formed between the isolation flange 42 and thebase flange 16 b. A flow outlet for making the first gas flow into thereaction furnace is formed by this clearance C1, in the small chamber43. A slight clearance C2 of approximately 1 to 3 millimeters is formedbetween the isolation flange 42 and the protrusion 16 c. An outflowpassage 42 a is formed by these clearances C1 and C2 for allowing a gassupplied into the small chamber 43 to flow into the processing chamber14 of the reaction furnace 39.

The boat 21 for holding the wafers 1 as the substrates for processing,is supported by the rotating shaft 41 and vertical and upright along thecenterline of the seal cap 20. The boat 21 is totally made of quartz orsilicon carbide. The boat 21 is made up of a pair of end plates 22, 23above and below, and multiple (three members in the figure) supportmembers 24 installed perpendicularly between the pair of end plates 22,23. Multiple lined support grooves 25 are formed longitudinally andmutually facing each other at equidistant spaces in each support member24. The outer circumferential edge of the support surface made up of theupward facing surface of each support groove 25 is radially chamfered.The curvature radius of the radial chamfering is set at one or moremillimeters. A protrusion in a semispherical shape is formed in thecenter section of the support surface. The outer circumferential sectionof the wafers 1 are inserted into the same stage of the support groove25 between the multiple support members 24. The protrusions on thesupport surface receive and support the lower circumferential surface atmultiple points (three locations in the figure). The multiple wafers 1respectively supported by each support groove 25 are arrayedhorizontally and mutually centered in the boat 21. As shown in FIG. 2,multiple heat blocking plates 26 are supported while arrayedhorizontally and mutually centered in a specified region on a side lowerthan the section facing a heater unit 30 on the lower section of theboat 21. The boat 21 is supported by the rotating shaft 41 installed topass through the seal cap 20. The boat 21 is rotated by the rotationmechanism 40.

The heater unit 30 for heating the interior of the process tube 11 onthe outer section of the outer tube 13, is installed concentrically soas to enclose the periphery of the outer tube 13. The heater unit 30 isstructured to heat uniformly over the entire of the process tube 11 orheat to a preset temperature distribution. The heater unit 30 isinstalled perpendicularly and supported by the case 31 of the CVDdevice. The reaction furnace 39 is mainly comprised of this heater unit30, and the process tube 11 including the previously mentioned innertube 12 and outer tube 13, and the furnace opening flange 16 includingthe inlet flange 16 a and the base flange 16 b.

As shown in FIG. 1, the case 31 is provided with a heater unitinstallation chamber 32 and a standby chamber 33 for standby during theloading/unloading of the boat 21 to and from the processing chamber 14.The standby chamber 33 is the load-lock type (A method for isolating theprocessing chamber and loading/unloading chamber using an isolationvalve such as a gate valve, to prevent air from flowing into theprocessing chamber, and stabilizing the processing by reducing externaldisturbances such as temperature and pressure.) and capable of raising avacuum. An exhaust tube 34 for exhausting the standby chamber 33, and anitrogen gas feed pipe 35 for supplying nitrogen (N2) gas as the purgegas to the standby chamber 33, are each connected on the side wall ofthe standby chamber 33 of the case 31. A wafer loading/unloading opening(not shown in drawing) opened and closed by the gate valve, is formed inthe other side wall of the standby chamber 33. A boat elevator (notshown in drawing) for raising and lowering the seal cap 20 is installedin the interior of the standby chamber 33.

As one process in the semiconductor device manufacturing method, thefilm forming method for the process of forming a thin film on the waferis described next, using the upright thermal CVD device.

As shown in FIG. 1, in the wafer charging step where multiple wafers 1are loaded in the boat 21, the boat 21 is in standby in the standbychamber 33. The multiple wafers 1 are loaded in the boat 21 by the wafertransfer equipment. The standby chamber 33 is purged at this time bynitrogen gas supplied from the nitrogen gas supply tube 35.

In the boat loading step for loading the boats 21 loaded with aspecified number of wafers 1 into the processing chamber 14, the boat 21is lifted by the boat elevator, the boat 21 is loaded from the furnaceopening 15 of the inner tube 12 into the processing chamber 14 of thereaction furnace 39, and as shown in FIG. 2, is placed in the processingchamber 14 in a state supported via the rotating shaft 41 by the sealcap 20 with the furnace opening 15 sealed hermetically.

In the state where the boat 21 is placed in the processing chamber 14 ofthe reaction furnace 39, the seal cap 20 makes direct contact with thebase flange 16 b via the O-ring 20 a, so that the small chamber 43 isformed by the bottom surface of the isolation flange 42 and the topsurface of the seal cap 20 and the inner circumferential surface of thebase flange 16 b. A clearance C1 is formed between the outercircumferential surface of the isolation flange 42 and the innercircumferential surface of the base flange 16 b. A clearance C2 isformed between the top surface of the isolation flange 42 and theprotrusion 16 c on the upper edge of the inner circumferential surfaceof the base flange 16 b. These clearances C1 and C2 form the outflowpassage 42 a for allowing gas supplied inside the small chamber 43 toflow into the processing chamber 14. The gas feed pipe 19 b installed inthe base flange 16 b connects to the small chamber 43.

In the step for processing the wafer 1 held by the boat 21 in theprocessing chamber 14, an exhaust pump is connected to the exhaust pipe17 for evacuating the interior of the processing chamber 14 to aspecified vacuum intensity (13.3 to 133 Pa). The heater unit 30 heatsthe processing chamber to raise the temperature of the wafer 1 to aspecified temperature (700 to 800° C., for example 750° C.) The boat 21supporting the wafer 1 is in this case rotated by the rotation mechanism40 by way of the rotating shaft 41. When the interior of the processingchamber 14 stabilizes to a specified vacuum intensity and temperature ofthe wafer 1 has stabilized at a specified temperature, the processinggas is then supplied to the processing chamber 14 by the gas feed pipes19 a, 19 b.

More specifically, as shown in FIG. 3B, NH3 gas G1 is supplied as thefirst gas from the feed opening of the gas feed pipe 19 b installed onthe lower section of the side wall of the base flange 16 b, to the smallchamber 43 formed by the inner circumferential surface of the baseflange 16 b and the top surface of the seal cap 20 and the bottomsurface of the isolation flange 42. The NH3 gas G1 supplied to thissmall chamber 43 flows from the flow opening of the clearance C1 formedbetween the outer circumference of the isolation flange 42 and the innercircumference of the base flange 16 b, to the outflow passage 42 aformed by the clearances C1, C2 formed between the isolation flange 42and the base flange 16 b and the protrusion 16 c, and is supplied fromthis outflow passage 42 a to the processing chamber 14 side. The SiH2Cl2gas G2 as the second gas on the other hand, is supplied from the feedopening for the gas feed pipe 19 a installed on the lower section on theside wall of the inlet flange 16 a to the processing chamber 14. The NH3gas G1 is in this case preferably supplied to the reaction furnacebefore the SiH2Cl2 gas G2. In other words, the relatively inert gas NH3gas G1 preferably purges the furnace opening flange 16 and the furnaceopening 15 and the interior of the reaction furnace 39 prior tosupplying the relatively activated SiH2Cl2 gas G2 to the reactionfurnace 39.

The process gas comprised of the SiH2Cl2 gas G2 and NH3 gas G1, risesinside the processing chamber 14 of the inner tube 12. This process gasflows downstream from the upper edge opening of the inner tube 12 andthrough the exhaust path 18 formed by the clearance between the innertube 12 and the outer tube 13, and is evacuated from the exhaust pipe17. The processing gas comprised of the SiH2Cl2 gas G2 and NH3 gas G1flows onto the wafer 1 heated to the film forming temperature, and asilicon nitride film (Si3N4) is formed by the thermal CVD method.

The supply of process gas comprised of the SiH2Cl2 gas G2 and NH3 gas G1stops when a preset processing time elapses (silicon nitride film hasdeposited to a specified film thickness), and the processing chamber 14is purged by an inert gas such as nitrogen (N2) gas. The N2 gas is atthis time supplied from the gas feed pipe 19 a or/and the gas feed pipe19 b. Residual gas in the processing chamber 14 is removed by purgingwith the N2 gas. When the boat 21 stops rotating, the seal cap 20 lowersand the furnace opening 15 of the processing chamber 14 opens, and thegroup of wafers 1 held in the boat 21 are unloaded from the furnaceopening 15 to outside the process tube 11 (boat unloading).

In the film forming process of the prior art, the feed openings of thegas feed pipes 19 a, 19 b for supplying SiH2Cl2 gas and NH3 gas were allprovided in the side wall of the inlet flange 16 a, so that byproductssuch as NH4Cl (ammonium chloride) were generated in the vicinity of thefurnace opening 15 in the lower section of the reaction furnace 39.These byproducts adhered to the low temperature sections on the wallsurfaces in the vicinity of the furnace opening 15, and adhered inparticular to the upper surface of the seal cap 20, and to the clearancebetween the seal cap 20 and the rotating shaft 41. When these byproductsform particles and adhere to the upper surface of the wafer 1, theycause a drop in productivity when using the semiconductor devicemanufacturing method.

The present embodiment however prevents byproducts from adhering in thevicinity of the furnace opening 15 on the lower section of the reactionfurnace 39. In other words, as shown in FIG. 3B, along with the NH3 gasG1 being fed into the small chamber 43 formed covering the upper surfaceof the seal cap 20 by the inner circumferential surface of the baseflange 16 b and the lower surface of the isolation flange 42, the NH3gas G1 that was fed into the small chamber 43, also flows from theoutflow passage 42 a formed by the slight clearance between theisolation flange 42, the base flange 16 b and the protrusion 16 c to theprocessing chamber 14 side so that the NH3 gas G1 purges the smallchamber 43. Also, the SiH2Cl2 gas G2 is supplied to the upper side ofthe isolation flange 42 or in other words is supplied downstream of theNH3 gas G1 flow. The SiH2Cl2 gas G2 is in this way prevented fromflowing into the small chamber 43, and byproducts such as NH4Cl does notadhere to low temperature sections (section below 150° C.) such as theseal cap 20, the clearance between the seal cap 20 and the rotatingshaft 41 and the inner side walls of the base flange 16 b. Moreover, thereaction of the SiH2Cl2 with the NH3 occurs on the upper section of thefurnace opening 15 and the temperature of the inlet flange 16 a is at alevel (200° C. or more) where the NH4Cl does not adhere, and thereforebyproducts will also not adhere to the inlet flange 16 a. The forming ofa source that emits particles can be prevented, and an unexpected dropin productivity in the semiconductor manufacturing process due toparticle emission can also be prevented.

Incidentally, the upper temperature of the isolation flange 42 in theabove described film forming step is a temperature of 200° C. or higherat which the NH4Cl does not adhere to the wall surfaces. However thelower temperature of the isolation flange 42 is 150° C. or less which isa temperature where the NH4Cl adheres to the wall surfaces.

The stainless steel is chemical affected by the SiH2Cl2 so that when theSiH2Cl2 gas G2 comes in contact with the stainless steel seal cap 20,there is the worry that the wafer will be contaminated by emission ofmetal (such as iron or chromium) substances due to the chemical effectson the seal cap 20.

In the present embodiment, the SiH2Cl2 gas G2 as was already described,does not come in contact with the seal cap 20, because the SiH2Cl2 gasG2 does not enter the small chamber 43. Therefore, the seal cap 20 isnot chemically affected by the SiH2Cl2 gas G2 even if the seal cap 20 ismade of stainless steel. In other words, metal that might causecontamination of the wafer is not emitted from the seal cap 20, even incases where the seal cap 20 is made from stainless steel.

In the present embodiment, the isolation flange 42 that covers the sealcap 20 is formed from a high nickel alloy that is highly resistant tocorrosion as previously described, so that metal that might causecontamination of the wafer is not emitted even if SiH2Cl2 gas G2 makescontact with the isolation flange 42.

The second embodiment of the present invention shown in FIG. 4 and FIG.5 is described next.

Structural parts in the present embodiment that are equivalent to thosein the previous embodiment are assigned the same reference numerals andtheir description is omitted.

An upper divider ring section 61 is provided continuously across theentire circumference below an inner tube mount 16 d of the furnaceopening flange 16. A boat lower flange 62 on the other side, isinstalled concentrically with a boat mount 49 on the lower surface ofthe boat mount 49 horizontally supported on the top edge of the rotatingshaft 41. The boat lower flange 62 is formed in a ring shape utilizing ahigh nickel alloy (for example high nickel alloys of 50 percent or morenickel, 15 to 30 percent chromium, and 15 to 30 percent molybdenum) withhigh corrosion resistance. A lower divider ring section 63 is formedfacing the upper divider ring section 61 on the bottom end of the boatlower flange 62. The upper divider ring section 61 and the lower dividerring section 63 overlap while maintaining a necessary clearance in aspecific width. The upper divider ring section 61 and the lower dividerring section 63 make up a cover 64 for covering the entire seal cap 20.A small chamber 43A is formed separate from the processing chamber 14 bythe cover 64 on the section below the furnace opening flange 16.

As shown in FIG. 5, a labyrinth seal section 65 is formed as a radiallywinding clearance in the section where the upper divider ring section 61and the lower divider ring section 63 overlap. In other words,ring-shaped protruding pieces 63 a, 63 b are formed concentrically onthe upper surface of the lower divider ring section 63. Ring grooves 61a, 61 b are formed concentrically with the ring-shaped protruding pieces63 a, 63 b on the lower surface of the upper divider ring section 61.The ring-shaped protruding pieces 63 a, 63 b fit into the ring grooves61 a, 61 b by way of the radial clearance C1 and the axial clearance C2.The labyrinth seal section 65 winding radially is comprised of the gapmade up of the clearances C1 and C2 between the ring-shaped protrudingpieces 63 a, 63 b, and the ring grooves 61 a, 61 b. The dimensions ofthe clearances C1 and C2 of the labyrinth seal section 65 are set withina range allowing mutual rotation by the upper divider ring section 61and the lower divider ring section 63, and set to a minimum dimension toprevent gas from passing between the small chamber 43A and theprocessing chamber 14, and to allow outflow of the NH3 gas describedlater. The labyrinth seal section 65 in other words forms an outflowpassage with an outflow passage outlet for allowing the first gassupplied to the small chamber 43A to flow into the reaction furnace. Theclearances C1 and C2 of the labyrinth seal section 65 are for exampleset to dimensions of 0.5 to 3 millimeters.

The function is described next. The wafer processing is the same as theprevious embodiment so a description is omitted.

When the boat 21 loaded with wafers is loaded into the processingchamber 14, the seal cap 20 closes to seal the lower end opening of thefurnace flange opening 16 hermetically. In this state, the upper dividerring section 61 and the lower divider ring section 63 overlap with thelabyrinth seal section 65, and the small chamber 43A is formed betweenthe boat mount 49, the upper divider ring section 61, the lower dividerring section 63, and the seal cap 20.

In the film forming step as shown in FIG. 5B, the NH3 gas G1 is suppliedas the first gas, from the gas feed pipe 19 b to the small chamber 43Aand the SiH2Cl2 gas G2 is supplied as the second gas, from the gas feedpipe 19 a to the processing chamber 14. The labyrinth seal section 65connects the small chamber 43A with the processing chamber 14 and formsa path for flow of the NH3 gas G1 to the processing chamber 14. The NH3gas G1 flows along the labyrinth seal section (outflow path) 65, andflows from the entire circumference of the upper divider ring section 61to the processing chamber 14.

The exhaust pipe 17 evacuates the processing chamber 14 so that theprocessing chamber 14 forms an upward gas flow. The labyrinth sealsection 65 winds radially and the resistance of this path restricts theflow of SiH2Cl2 gas G2 into the small chamber 43A.

The C1 and C2 clearance dimensions, the radial length and the number ofwindings of the labyrinth seal section 65 are set to achieve a statewhere SiH2Cl2 gas G2 does not flow into the small chamber 43A. If the C1and C2 clearances are made sufficiently small, then the ring-shapedprotruding pieces 63 a, 63 b of the lower divider ring section 63 aswell as the ring grooves 61 a, 61 b of the upper divider ring section 63or in other words the labyrinth seal section 65 maybe eliminated.

Incidentally, separating the seal cap 20 from the heater unit 30 causesa low temperature (below 150° C.) to be reached where NH4Cl is emitted.Therefore when the NH3 gas G1 and the SiH2Cl2 gas G2 mix in the vicinityof the seal cap 20, the NH4Cl adheres to and accumulates on the surfaceof the seal cap 20, etc. The present embodiment suppresses a reactionbetween the NH3 gas G1 and the SiH2Cl2 gas G2 in the low temperaturesection comprised by the small chamber 43A, comprised by the smallclimber 43A, by supplying NH3 gas G1 to the small chamber 43A separatingfrom the processing chamber 14, and supplying SiH2Cl2 gas G2 to theprocessing chamber 14 side. NH4Cl is in this way prevented from beinggenerated in low temperature sections. Moreover, byproducts such asNH4Cl that results from reactions are prevented from adhering to anddepositing on the seal cap 20 and the furnace opening flange 16.

The present embodiment prevents reaction byproducts from adhering to thelow temperature sections of the furnace opening flange 16 so thatservicing of the furnace opening such as cleaning of the furnace openingflange 16 can be drastically reduced, and routine servicing can beperformed at longer intervals. For example, service tasks that wereperformed at intervals of approximately one month, can in thisembodiment be extended to once every three months or once a year.

The NH3 gas and the SiH2Cl2 gas can be separated in the low temperaturesection so that the installation position and shape of the upper dividerring section 61 and the lower divider ring section 63 need not berestricted to those described in the present embodiment. For example,the lower divider ring section 63 may be installed onto the rotatingshaft 41, and may be installed on the seal cap 20.

The third embodiment of the present invention is described next as shownin FIG. 6 and FIG. 7.

Structural parts in the present embodiment that are equivalent to thosein the previous embodiment are assigned the same reference numerals andtheir description is omitted.

A protrusion 12 a connecting across the entire circumference is providedon the outer circumferential surface of the bottom end of the inner tube12. Installing the protrusion 12 a on an inner tube mount 16 dconnecting across the entire circumference on the internal circumferenceof the furnace opening flange 16, makes the inner tube 12 support on thefurnace opening flange 16. An extending section 12 b extends below theprotrusion 12 a of the inner tube 12. A divider ring 27 made from quartzglass or silicon carbide (SiC) is installed as a ring-shaped platemember below the extending section 12 b on the seal cap 20. The dividerring 27 is secured to the seal cap 20 by a clamp ring 28. The clearances29 a, 29 b of approximately 0.1 to 3 millimeters form a sealingmechanism (labyrinth seal) between the divider ring 27 and the extendingsection 12 b of the inner tube 12, and between the divider ring 27 andthe end plate 23 of the boat 21. The dimensions of the clearances 29 a,29 b are preferably 2 millimeters or less.

In the state where the boat 21 is loaded into the processing chamber 14of the reaction furnace 39, a small chamber (hereafter, called thesecond small chamber) 47 is formed by the seal cap 20 and the furnaceopening flange 16 and the extending section 12 b of the inner tube 12and the divider ring 27. One end of a gas feed pipe (hereafter calledthe second gas feed pipe) 19 a for supplying the second gas is connectedto the second small chamber 47. The other end of the second gas feedpipe 19 a is connected to a supply source (not shown in drawing) for thesecond gas such as SiH2Cl2 gas or inert gas. The opening at the tip(blow vent) of the second gas feed pipe 19 a therefore forms a feedopening for supplying the second gas into the reaction furnace.

Also in the state where the boat 21 is loaded into the processingchamber 14 of the reaction furnace 39, a small chamber (hereafter,called the first small chamber) 45 is formed by the seal cap 20 and thedivider ring 27, and the end plate 23 on the lower side of the boat 21and the boat mount 49. A gas feed pipe (hereafter called a first gasfeed pipe) 19 b for supplying a first gas connects to the first smallchamber 45 via a space 59 and a clearance 50. A clearance 29 b is formedbetween the end plate 23 on the lower side of the boat 21 and thedivider ring 27. A flow outlet 46 b is formed by the clearance 29 b forallowing the gas supplied to the first small chamber 45 to flow into theprocessing chamber 14 of the reaction furnace 39. A clearance 29 a isformed between the extending section 12 b of the inner tube 12 and thedivider ring 27. A flow outlet 46 a is formed by the clearance 29 a forallowing the gas supplied to the second small chamber 47 to flow intothe processing chamber 14 of the reaction furnace 39.

A housing 53 of the rotation mechanism 40 is fastened by way of the baseflange 51 to the seal cap 20. A gear case 52 is fastened at the bottomend of the housing 53. A lower section rotating shaft 55 is installed onthe housing 53 for free rotation via a shaft bearing 54. The bottom endof the lower section rotating shaft 55 is exposed into the interior ofthe gear case 52. A worm wheel 56 is installed at the bottom end of thelower section rotating shaft 55. A worm 57 is installed on the wormwheel 56 for free rotation on the gear case 52. The rotating shaft 58 ofthe worm 57 connects to a boat rotation motor not shown in the drawing.

The rotating shaft 41 passing through the seal cap 20 is affixed in thespace 59 concentrically with the lower section rotating shaft 55. Theboat mount 49 is installed at the upper end of the rotating shaft 41.The boat 21 is set and clamped on the boat mount 49. The desiredclearance 50 is formed between the seal cap 20 and the base flange 51and the rotating shaft 41. A gas feed path 44 passing through the space59 is formed in the side surface of the base flange 51. The first gasfeed pipe 19 b is connected to the gas feed path 44, and therefore thegas feed path 44 connects to a supply source (not shown in drawing) suchas inert gas or NH3 gas as the first gas. The space 59 is formedadjacent to the rotating shaft 41 below the seal cap 20, and connects tothe gas feed path 44 and the space 50. Therefore the opening on thedownstream side of the clearance 50 forms a feed opening for supplyingthe first gas to the first small chamber 45.

The function is described next. The wafer processing is the same as theprevious embodiment so a description is omitted.

When the boat 21 loaded with wafers is loaded into the processingchamber 14, the seal cap 20 closes to seal the lower end opening of thefurnace opening flange 16 hermetically. In this state, the first gasfeed pipe 19 b installed on the side wall of the base flange 51 connectsvia the space 59 and the clearance 50 to the first small chamber 45enclosed by the seal cap 20 and the divider ring 27 and the end plate 23on the lower side of the boat 21 and the boat mount 49.

In the step for processing the wafer 1 supported in the boat 21 in theprocessing chamber 14, the boat 21 holding the wafer 1 is rotated by therotating shaft 41 of the rotation mechanism 40. When the interior of theprocessing chamber 14 is stabilized at a specified vacuum intensity, andwhen the temperature of the wafer 1 stabilizes to the specifiedtemperature, the process gas is supplied from the gas feed pipes 19 a,19 b to the processing chamber 14.

More specifically, NH3 gas G1 as shown in FIG. 7, is supplied as thefirst gas from the first gas feed pipe 19 b connected to the side wallof the base flange 51, via the gas feed path 44 to the space 59, andfrom the space 59 flows via the clearance 50 from the feed opening ofthe clearance 50 to the first small chamber 45. The NH3 gas G1 suppliedto the first small chamber 45, is supplied to the processing chamber 14from the flow outlet 46 b comprised of the clearance 29 b formed betweenthe divider ring 27 and the end plate 23 on the lower side of the boat21. The SiH2Cl2 gas G2 is supplied as the second gas from the feedopening of the second gas feed pipe 19 a connected to the lower sectionon the side wall of the furnace opening flange 16, to the second smallchamber 47 enclosed by the seal cap 20 and the furnace opening flange 16and the extending section 12 b of the inner tube 12 and the divider ring27. The SiH2Cl2 gas G2 supplied to this second small chamber 47 issupplied to the processing chamber 14 from the flow outlet 46 acomprised of the clearance 29 a formed between the divider ring 27 andthe extending section 12 b of the inner tube 12. In this case, NH3 gasG1 is supplied to the reaction furnace 39 prior to the SiH2Cl2 gas G2.In other words, the furnace opening section and the interior of thereaction furnace 39 is preferably purged with NH3 gas G1 beforesupplying the SiH2Cl2 gas G2.

The present embodiment can prevent reaction byproducts such as NH4Clfrom adhering to sections in the vicinity of the furnace opening flange15 of the reaction furnace 39 in the film forming step. In other words,as shown in FIG. 7, the NH3 gas G1 is supplied to the first smallchamber 45 enclosed by the seal cap 20 and the divider ring 27 and theend plate 23 on the lower side of the boat 21, and the boat mount 49 viathe slight clearance 50 between the rotating shaft 41 and the seal cap20, and the supplied NH3 gas G1 diffuses (is supplied) to the processingchamber 14 from the flow outlet 46 b comprised of the clearance 29 b. Inother words, the NH3 gas G1 purges the first small chamber 45. Also, theSiH2Cl2 gas G2 is supplied into the second small chamber 47 enclosed bythe seal cap 20 and the furnace opening flange 16 and the extendingsection 12 b of the inner tube 12 and the divider ring 27, and thesupplied SiH2Cl2 gas G2 is supplied into the processing chamber 14 fromthe flow outlet 46 a made up of the slight clearance 29 a. In otherwords, the SiH2Cl2 gas G2 purges the second small chamber 47. The inflowof SiH2Cl2 gas G2 into the first small chamber 45 is in this wayrestricted, and the inflow of NH3 gas G1 into the second small chamber47 is in this way restricted so that byproducts such as NH4Cl areprevented from adhering to the upper surface of the seal cap 20 and theclearance 50 between the seal cap 20 and the rotating shaft 41, and theinner circumferential surface of the furnace opening flange 16.

The processing chamber 14 where the NH3 gas G1 as the first gas flowingout from the first flow outlet 46 b, mixes and reacts with the SiH2Cl2gas G2 as the second gas flowing out from the second flow outlet 46 a iscomprised of the divider ring 27 and the inner tube 12 and the outertube 13 and the end plate 23 on the lower side of boat 21. Thesecomponents are all made from non-metallic materials such as quartz. Nometallic members are used in the processing chamber 14 so that nometallic contamination occurs.

Moreover, providing an extending section 12 b extending downwards fromthe protrusion 12 a, to install the inner tube 12 in the furnace openingflange 16, results in only a slight clearance 29 a between the dividerring 27 and the extending section 12 b of the inner tube 12. This slightclearance 29 a prevents the NH3 gas G1 from flowing into the secondsmall chamber 47, and makes it difficult for byproducts to adhere to theinner circumferential surface of the furnace opening flange 16.

The fourth embodiment of the present invention is described next whilereferring to FIG. 8.

The present embodiment differs from the third embodiment in the pointthat a gas feed pipe 19 c (Hereafter called the third gas feed pipe.)for supplying the third gas G3 to the processing chamber 14 is insertedinto the furnace opening flange 16. The gas feed opening of the tipopening (blow vent) of the third gas feed pipe 19 c is installeddownstream (upwards) of the flow outlet 46 a, 46 b. Gas supplied fromthe gas feed opening of the third gas feed pipe 19 c mixes downstream ofthe flow outlets 46 a, 46 b with the gas flowing from the flow outlets46 a, 46 b.

The third embodiment contains the additional third gas feed pipe 19 cand can therefore handle three or more types of gases.

When using two types of gases, the same gas is preferably supplied fromthe first gas feed pipe 19 b and the second gas feed pipe 19 a, whilethe other gas is supplied from the third gas feed pipe 19 c.

For example when using NH3 gas and SiH2Cl2 gas as the same as in thethird embodiment, the NH3 gas which has relatively little chemicaleffect on metal members is supplied from the first gas feed pipe 19 band from the second gas feed pipe 19 a, and the SiH2Cl2 gas (corrosivegas) which tends to easily apply chemical effects to metal members issupplied from the third gas feed pipe 19 c. The SiH2Cl2 gas which is acorrosive gas therefore only comes in contact with non-metallic membersuch as quartz and never makes contact with metal members. Metalliccontamination occurring due to corrosive gas contacting metal member cantherefore be reliably prevented. The fourth embodiment that emphasizespreventing metal contamination is in this point more advanced than theother embodiments that center mainly on preventing NH4Cl from adheringto low temperature sections such as the rotating shaft and the topsurface of the seal cap.

The fifth embodiment of this invention is described next while referringto FIG. 9.

Structural parts in the present embodiment that are equivalent to thosein the previous embodiment are assigned the same reference numerals andtheir description is omitted.

One end of the gas feed pipe 19 a below the inner tube mount 16 d of thefurnace opening flange 16, connect to the first small chamber 45A whichis enclosed by the seal cap 20 and the furnace opening flange 16 and theboat mount 49. A supply source (not shown in drawing) for a second gassuch as inert gas or SiH2Cl2 gas, connects to this gas feed pipe 19 a.The tip opening (blow vent) of the gas feed pipe 19 a therefore forms afeed opening for supplying the second gas to the first small chamber 45.

The housing 53 of the rotation mechanism 40 is fastened by way of thebase flange 51 to the seal cap 20. A gear case 52 is fastened at thebottom end of the housing 53. A lower section rotating shaft 55 isinstalled on the housing 53 for free rotation via a shaft bearing 54.The bottom end of the lower section rotating shaft 55 is exposed intothe interior of the gear case 52. The worm wheel 56 is installed at thebottom end of the lower section rotating shaft 55. The worm 57 isinstalled on the worm wheel 56 for free rotation in the gear case 52.The rotating shaft 58 of the worm 57 connects to a boat rotation motornot shown in the drawing.

The rotating shaft 41 passing through the seal cap 20 is affixed in thespace 59 concentrically with the lower section rotating shaft 55. Theboat mount 49 is installed at the upper end of the rotating shaft 41.The boat 21 is set and clamped on the boat mount 49. The desiredclearance 50 is formed between the seal cap 20 and the base flange 51and the rotating shaft 41. A gas feed path 44 passing through the space59 is formed in the side surface of the base flange 51. The first gasfeed pipe 19 b is connected to the gas feed path 44, and therefore thegas feed path 44 connects to a supply source (not shown in drawing) suchas inert gas or NH3 gas as the first gas. The space 59 is formedadjacent to the rotating shaft 41 below the seal cap 20, and connects tothe gas feed path 44 and the clearance 50. The opening on the downstreamside of the clearance 50 therefore forms a feed opening for supplyingthe first gas to the first small chamber 45.

The function is described next. The wafer processing is the same as theprevious embodiment so a description is omitted.

When the boat 21 holding the wafers is loaded into the processingchamber 14, the seal cap 20 closes to seal the lower end opening of thefurnace opening flange 16 hermetically. In this state, the first gasfeed pipe 19 b connected to the side wall of the base flange 51 connectsvia the space 59 and the clearance 50 to the first small chamber 45Aenclosed by the seal cap 20 and the furnace opening flange 16 and theboat mount 49.

In the step for processing the wafer 1 supported in the boat 21 in theprocessing chamber 14, the boat 21 holding the wafer 1 is rotated by therotating shaft 41 of the rotation mechanism 40. When the interior of theprocessing chamber 14 is stabilized at a specified vacuum intensity, andwhen the temperature of the wafer 1 stabilizes to the specifiedtemperature, the process gas is supplied from the gas feed pipes 19 a,19 b to the processing chamber 14.

More specifically, the NH3 gas G1, as shown in FIG. 9, is supplied asthe first gas from the first gas feed pipe 19 b connected to the sidewall of the base flange 51, via the gas feed path 44 to the space 59,and from the space 59 flows via the clearance 50 to the first smallchamber 45A. The NH3 gas G1 supplied to the first small chamber 45A, issupplied to the processing chamber 14. Also, the SiH2Cl2 gas G2 as thesecond gas is supplied from the second gas feed pipe 19 a connected tothe lower section on the side wall of the furnace opening flange 16, tothe first small chamber 45A. The NH3 gas G1 is in this case supplied tothe reaction furnace 39 prior to the SiH2Cl2 gas G2. In other words, theinterior of the reaction furnace 39 and furnace opening section arepreferably purged with NH3 gas G1 before supplying the SiH2Cl2 gas G2.

The present embodiment can prevent NH4Cl byproducts from adhering tosections in the vicinity of the furnace opening 15 of the reactionfurnace 39 in the film forming step. In other words, the NH3 gas G1 issupplied to the first small chamber 45A enclosed by the seal cap 20 andthe furnace opening flange 16 and the boat mount 49 via the slightclearance 50 between the rotating shaft 41 and the seal cap 20, and thesupplied NH3 gas G1 diffuses (is supplied) to the processing chamber 14.The SiH2Cl2 gas G2 therefore cannot easily flow into the rotationmechanism 40 and elsewhere due to the outflow of NH3 gas G1 from theslight clearance 50 of the rotating shaft 41, so that byproducts such asNH4Cl can be prevented from adhering to the clearance 50 at the rotatingshaft 41.

This invention is not limited by the above embodiments and needless tosay, changes of different types not departing from the spirit and thescope of this invention are allowed.

For example, this invention is not limited to the process for formingSi3N4 film and film forming processes for other films may be utilized.

When forming the SiO2 film (LTO (low temperature oxide) film) usingsilane (SiH4) and oxygen (O2), the O2 gas may be used as the first gas,and the SiH4 gas may be used as the second gas.

Moreover, this invention can be applied to self-cleaning (task ofremoving byproducts and film deposited on the reaction furnace andmembers inside the reaction furnace) using gases such as ClF3, NF3, F2.

The inert gas nitrogen (N2) gas or argon (Ar) gas may be used as thefirst gas, and the cleaning gases such as ClF3, NF3, F2 may be utilizedas the second gas. In this case, corrosion of the metal sections on thefurnace opening can be prevented.

This invention is further not limited to an upright thermal CVD devicecontaining a process tube made up of an inner tube and outer tube, andmay be utilized in other CVD devices comprising a process tubecontaining only an outer tube, or to diffusion devices or to oxidizingdevices.

A diffusion device for diffusing impurities may use a dilute gas ofnitrogen (N2) gas as the first gas, and impurity gas of PH3 gas or B2H6gas and AsH3 as the second gas.

An oxidizing device may use oxygen (O2) as the first gas, and hydrogen(H2) gas as the second gas.

1. A substrate processing apparatus comprising: a reaction furnace for processing a substrate which includes a process tube, an inlet flange for supporting the process tube, and a base flange for supporting the inlet flange; a seal cap for sealing the reaction furnace hermetically; a cover installed inside the base flange separately from the seal cap so as to cover approximately the entire surface of the seal cap facing the inner side of the reaction furnace; a small chamber formed by a space enclosed by the seal cap, the cover and the inner wall surface of the base flange; a feed opening facing the small chamber for supplying a first gas that is inert to the seal cap into the small chamber; a flow outlet formed by a clearance between the cover and the inner wall surface of the base flange, for making the first gas supplied to the small chamber flow into the reaction furnace; and a feed opening provided further downstream than the flow outlet, for supplying a second gas that is more active to the seal cap than the first gas into the reaction furnace.
 2. The substrate processing apparatus according to claim 1, wherein the feed opening for supplying the first gas is provided in the base flange; and the feed opening for supplying the second gas is provided in the inlet flange.
 3. The substrate processing apparatus according to claim 1, wherein a ring-shaped protrusion is formed protruding to the inner side on the upper section of the inner circumferential surface of the base flange, and the cover is installed below the protrusion at a position with somewhat of a clearance.
 4. The substrate processing apparatus according to claim 3, wherein the outer diameter of the cover is smaller than the inner diameter of the base flange, and larger than the inner diameter of the protrusion.
 5. The substrate processing apparatus according to claim 1, wherein the cover is formed by a plate-shaped member.
 6. The substrate processing apparatus according to claim 1, comprising a boat for holding multiple substrates approximately horizontally at intervals in multiple stages, and a rotation mechanism for supporting and rotating the boat by way of a rotating shaft penetrating through the seal cap, wherein the cover is installed in the rotating shaft.
 7. The substrate processing apparatus according to claim 1, wherein the cover is arranged below the bottom of the boat and separately from the bottom of the boat.
 8. The substrate processing apparatus according to claim 1, wherein the first gas is ammonia, the second gas is dichlorosilane, and the processing is a processing for forming a silicon nitride film on the substrate by a thermal CVD method.
 9. A semiconductor device manufacturing method comprising the steps of: loading a substrate into a reaction furnace which includes a process tube, an inlet flange for supporting the process tube, and a base flange for supporting the inlet flange; sealing the reaction furnace hermetically with a seal cap; processing the substrate by supplying a first gas that is inert to the seal cap from a feed opening facing a small chamber into the small chamber formed by a space enclosed by the seal cap, the inner wall surface of the base flange and a cover installed inside the base flange separately from the seal cap so as to cover approximately the entire surface of the seal cap facing the inner side of the reaction furnace, along with making the first gas supplied to the small chamber flow into the reaction furnace from a flow outlet formed by a clearance between the cover and the inner wall surface of the base flange, and supplying a second gas that is more active to the seal cap than the first gas into the reaction furnace from a feed opening provided further downstream than the flow outlet; and unloading the processed substrate from the reaction furnace. 